Project Summary/Abstract Traumatic brain injury is a significant health problem in a large number of military personnel returning from Iraq and Afghanistan. Unfortunately, many individuals with mild traumatic brain injuries stemming from exposure to blasts or other accidents do not get properly evaluated and treated, due to the subtle nature of their injuries. Moreover, the brain changes associated with mild traumatic brain injury often go undetected with standard brain imaging. Other issues, such as coexisting emotional disorders, the stigma of a possible mental disability, their young age, and the lack of awareness of such cognitive changes, can each affect outcome and further complicate recovery. The current study proposes to conduct a comprehensive battery of tests in returning veterans with mild traumatic brain injury in order to document impairments in cognitive skills, such as reasoning and problem solving. Such abilities are critical as our veteran patients attempt to return to work and school. In addition, we will use a recently developed form of MRI brain imaging, known as diffusion tensor imaging, which can identify subtle brain changes that are not detected with standard MRI scans. In this way, we will be able to identify cognitive deficits and their relationship to brain injury in this patient group. This study will help us to disentangle difficulties stemming from other co-existing symptoms, such as emotional disorders, versus those problems stemming directly from trauma to the brain. Improved diagnostics and treatment for our veteran patients with traumatic brain injury is critically needed. Data from this study will provide important information regarding the characteristic cognitive profile of patients with mild traumatic brain injury and provide direction for proper diagnostic and treatment procedures within the VA system. Moreover, findings from this study will clarify the brain basis of cognitive deficits in this patient group.